21551212 has 6 divisors (see below), whose sum is σ = 37714628. Its totient is φ = 10775604.

The previous prime is 21551177. The next prime is 21551221. The reversal of 21551212 is 21215512.

It is a self number, because there is not a number n which added to its sum of digits gives 21551212.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2693898 + ... + 2693905.

Almost surely, 2^21551212 is an apocalyptic number.

It is an amenable number.

21551212 is a deficient number, since it is larger than the sum of its proper divisors (16163416).

21551212 is a wasteful number, since it uses less digits than its factorization.

21551212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5387807 (or 5387805 counting only the distinct ones).

The product of its digits is 200, while the sum is 19.

The square root of 21551212 is about 4642.3282951554. The cubic root of 21551212 is about 278.2854924726.

Adding to 21551212 its reverse (21215512), we get a palindrome (42766724).

The spelling of 21551212 in words is "twenty-one million, five hundred fifty-one thousand, two hundred twelve".